In recent years considerable attention has been focused upon the development of polymers having high temperature reistance. While considerable success has been achieved in the synthesis of such polymers, it has been found that these polymers commonly are intractable and lack plastic flow characteristics normally encountered in polymers which lack high temperature resistance. Representative intractable polymers which lack a glass transition temperature below the decomposition temperature include the BBB type polymers [i.e. (poly(bisbenzimidazobenzophenanthroline) and related nitrogenous polymers]. Fibers and films routinely may be solution spun or cast from such high temperature resistant polymers. However, the intractable nature of such polymers has made the formation of quality three-dimensional shaped articles from the same difficult. For instance, when solid particles of an intractable polymer are hot pressed, good compaction commonly is achieved, but the resulting article commonly exhibits minimal particle bonding to other particles as well as to fibrous reinforcements thereby limiting its utilization to those applications where strength demands are not critical.
In an attempt to provide compositions having increased strength as well as high temperature resistance which are capable of being shaped by conventional forming methods certain cross-linkable polymers such as polybenzimidazoles (hereinafter PBI) have been admixed with a BBB type polymer base as described in U.S. Appln. Ser. No. 524,751, filed Nov. 18, 1971 issued as U.S. Pat. No. 3,987,015. However the strength of such alloyed compositions may be further enhanced in accordance with the teachings of the presently claimed invention. It has been observed that increases in strength could also be obtained by reinforcing the neat or BBB polymer which chopped BBB fibers as described in U.S. Pat. No. 3,505,277. However conventional methods for combining the resin polymer matrix and the chopped fibers do not generate adhesion between the fiber and the resin matrix and therefore the effect of the reinforcing fiber is substantially reduced.
It is an object of the present invention to improve the processability of normally intractable high temperature resistant polymers.
It is an object of the present invention to improve the processability of an intractable high temperature resistant polymer which lacks a glass transition temperature below its decomposition temperature.
It is an object of the present invention to provide an improved process for forming a three-dimensional shaped article from a normally intractable high temperature resistant polymer.
It is a further object of the present invention to improve the strength of three-dimensional articles formed from a hot pressed normally intractable high temperature resistant polymer.
It is a further object of the present invention to provide a process for reinforcing a normally intractable high temperature resistant polymer matrix or mixture of such polymer with cross-linkable polymer such as PBI with a high temperature resistant plasticized fiber in a manner sufficient to provide a strong adhesive attachment between the plasticized fiber and the polymer matrix which is deposited thereon in the form of a precipitate.
It is a further object of the present invention to provide a composition having a normally intractable high temperature resistant polymer matrix or mixture of such polymer with cross-linkable polymer such as PBI reinforced with a high temperature resistant plasticized fiber in a manner sufficient to provide a strong adhesive attachment between the plasticized fiber and the polymer matrix which is deposited thereon in the form of a precipitate.
These and other objects as well as the scope, nature, and utilization of the claimed invention will be apparent from the following description and appended claims.